HDAC6 and p300 Modulate GnRH Induced Acetylation of α Tubulin in Gonadotrope Cells

Presentation Number: SUN 494
Date of Presentation: April 2nd, 2017

Shaihla Amin Khan* and Amy Marie Navratil
University of Wyoming, Laramie, WY

Abstract

Microtubules (MT) are highly dynamic tubular filaments that are major component of the cytoskeleton. MTs are heterodimers that consist of α and β tubulin, which are responsible for supporting cellular structure and intracellular transport. It is well known that post translation modifications (PTMs) stabilize microtubules and may provide navigational cues for molecular motors. Intracellular cargo preferentially moves along microtubules that are marked by PTMs to facilitate delivery to specific subcellular domains. Acetylation is a major PTM that involves the donation of an acetyl group to lysine residues via acetyltransferases. Within MTs, α tubulin can be acetylated at lysine 40 but it is not known whether this modification occurs in gonadotrope cells of the anterior pituitary. To test this, we utilized the gonadotrope derived LβT2 cell line to address the temporal acetylation profile following GnRH agonist (GnRHa) treatment. Using an antibody that detects Lys40 acetylation on α-tubulin, we observed that GnRHa induced acetylation of tubulin was maximal at 60 and 90 minutes. Gonadotrope cells rapidly undergo cytoskeletal remodeling following GnRH treatment but at approximately 60 minutes, cells begin reducing their movements back to baseline. Thus, the later kinetics of microtubule acetylation are consistent with filament stabilization. Next, we identified the GnRH induced signaling pathways that are responsible for microtubule acetylation. We found that the MEK inhibitor PD98509 significantly decreases acetylated tubulin levels following 60 minutes of GnRHa treatment. Given the requirement of ERK in α tubulin acetylation, we addressed the role of the ERK dependent acetyl transferase p300. We found that the p300 inhibitor c646 also inhibited GnRH induced α tubulin acetylation. Taken together, these results suggest that GnRH induced ERK activation of p300/CBP can acetylate α tubulin. We next identified the deacetylase that was responsible for removing acetyl groups from α tubulin. We found that inhibition of histone deacetylase 6 (HDAC) rapidly lead to microtubule acetylation independent of GnRH treatment. These results suggest that HDAC6 can regulate acetylation of tubulin in gonadotrope cells. Collectively, our results indicate that GnRH can induce acetylation of α tubulin through ERK dependent activation of p300 acetyltransferase. We suggest acetylation may provide routing signals and stabilization to microtubules so they can effectively transport secretory vesicles to the membrane following a pulse of GnRH.

 

Nothing to Disclose: SAK, AMN